Casts and splints have traditionally been made by coating or impregnating a substrate, usually fabric, such as gauze, mesh, fiberglass or the like with a dry casting material such as Plaster of Paris or various resins. The coated substrate is then dipped in water or other liquid-activating substance to initiate the "setting" of the casting material, squeezed or wrung out to express excess water, placed on the appropriate part of the patient and allowed to cure.
The process is often messy, time consuming, requires multiple supplies and considerable skill. Wet casting material can be contacted with hands, clothes, patient, floor furniture and the like. Usually the person applying the cast or splint wears gloves and protective clothing and often uses a special "casting room." If colored compounds are used, messy stains may result. If resins are used, a detackifier may be necessary. Often, a protective layer of material is placed on the patient to protect the skin (see, for example, U.S. Pat. No. 4,193,395, which refers to covering the body part with a stockinette).
Some casting devices have been described, for example in U.S. Pat. Nos. 4,235,228, 4,442,833, 4,454,874, 4,628,917, 4,770,299, 4,869,046 and 4,899,738, which enclose the casting material in sleeves or coverings of various materials so that direct contact with the casting material is not necessary.
Even those devices that enclose the casting material still require immersing the device in water, wringing and applying. This results in a wet layer of material in direct contact with the patient's skin, which may be uncomfortable and irritating and can, in time, cause maceration and sloughing of the skin. This also requires a ready source of water, which may not be available in some circumstances.
Some devices have tried placing a totally moisture impermeable layer next to the skin, for example, U.S. Pat. No. 4,454,874. This may keep moisture from the casting material from contacting the skin; however, it traps moisture that is normally released from the skin in sweating and respiration of the skin. This moisture builds up under the impermeable layer and may cause tissue damage, odor and the like. Other, non-unitary devices have used a separate dry pad or layer to be applied to the patient or adhered to the casting device after the casting device or material is wetted such as, for example, U.S. Pat. Nos. 4,193,395 and 4,628,917. These latter devices require more than one component, and adhesives usually do not hold well in a moist environment and may restrict respiration of vapor.
Other devices have been described, for example in U.S. Pat. Nos. 4,770,299, 4,869,046 and 4,899,738, which use hydrophobic material on the patient contact side, but which still require immersing the device. The immersion and "squeezing" of the device results in water being trapped or retained in the spaces of the hydrophobic material which then presents a wet surface to the patient and may trap moisture next to the patient.
The most recent unitary devices which concern the moisture retention problem of prior art casting and splinting devices are described in U.S. Pat. Nos. 5,171,208 and 5,318,504. These devices provide a layer of water-impermeable, water vapor-permeable film on the side of the device in contact with the patient's skin. The film is placed next to the patient's skin to release trapped moisture while the cast or splint is in place on the patient, thus preventing water, or other liquid from penetrating through the device to contact the patient's skin while the device is curing or if the device is exposed to liquid. Next to the water impermeable film, is a layer of water-permeable padding followed by casting material and a non-woven water permeable film of, for example, polypropylene. The devices can also be made such that they are in a condition for application without the need to fully immerse the device in liquid. In such a case, the device is made with a pre-formed liquid-containing pouch formed of water permeable spun-bonded polypropylene.